Clinical Findings

• Consider in any individual, even if immunized
• Catarrhal period (1–2 weeks):
  • Illness onset insidious (coryza, mild fever, and nonproductive cough)
  • Infants can have apnea and respiratory distress
• Paroxysmal period (2–6 weeks):
  • Paroxysmal cough
  • Inspiratory “whoop"
    

    Stages of disease (weeks)

  • Posttussive vomiting
• Convalescent period (>2 weeks):
  • Paroxysms gradually decrease in frequency and intensity

Diagnosis

CDC Clinical Case Definition

• A clinical case is defined as a person:
  • Who has a cough illness lasting >2 weeks with one of the following (without other apparent cause)
    • paroxysms of coughing
    • inspiratory "whoop"
    • post-tussive vomiting
• Laboratory criteria for diagnosis are:
  • Positive nasopharyngeal culture
  • Positive PCR reaction assay from nasopharyngeal swab
• Confirmed case is defined as a person:
  • With an acute cough illness of any duration who is culture positive
  • Who meets the clinical case definition with laboratory confirmation by PCR
  • Who meets the clinical case definition and is epidemiologically linked directly to a case confirmed by either culture or PCR
• Probable case is defined as a person:
  • Who meets the clinical case definition without laboratory confirmation or an epidemiologic link to a laboratory-confirmed case

Pertussis Laboratory Testing

Note

• Obtain PCR and culture with Dacron nasopharyngeal swabs or nasopharyngeal aspirate; swabbing throat and/or anterior nose yields unacceptable levels of recovery.
• Pertussis DFA lacks sensitivity and specificity, should not be used as a replacement for culture, and is not recognized by CDC for confirmation of diagnosis
• IgG level to pertussis antigen - either pertussis toxin (PT) which is most sensitive/specific, or filamentous hemaggutinin (FHA)
  • Methods:
    • Paired sera method: obtain acute level (within 2 weeks of cough) and convalescent level (4-6 weeks later); 4-fold increase confirms acute infection
    • Single sera method: a single high antibody titer obtained ideally >4 weeks after cough onset may suggest infection
  • IgG to pertussis FHA may be useful for B. parapertussis infection (IgG to PT is specific to B. pertussis)
  • Recent vaccination with pertussis and post-vaccination antibody levels do not interfere with diagnosis

Optimal Timing for Testing

Treatment

• Treat persons aged >1 year within 3 weeks of cough onset.
• Treat infants aged <1 year within 6 weeks of cough onset.
• Postexposure prophylaxis: administer course of antibiotic (same doses as in treatment schedule) to close contacts within 3 weeks of exposure, especially in high-risk settings

References